The hardness of a material is of particular relevance for mechanical engineering and the processing industry. As a characteristic property, the hardness of a material determines its resistance to mechanical impact and wear. The hardness of materials, components and (machine) tools is decisive for their performance and durability. Hardness is therefore an essential quality criterion in manufacturing.
Conventionally, the hardness of a material is determined by a penetration test. However, the methods for measuring the indentation hardness are destructive methods which damage or render unusable the material to be tested. These are therefore usually only used on a random basis. In times of digitalization and automation of manufacturing processes, a 100% inspection and complete documentation of the quality gains in importance. This is where the micromagnetic measuring method developed by QASS for non-destructive hardness testing comes in.
Barkhausen noise is a physical effect that only occurs with ferromagnetic materials when they are magnetized by an external magnetic field. If the field strength of the external magnetic field is increased, the magnetization of the material does not increase steadily, but discreetly in Barkhausen jumps.
The reason for this lies in the microstructure of ferromagnetic materials. These materials consist of a multitude of microscopically small areas, which are regarded as elementary magnets. These are called magnetic domains and were discovered by the French physicist Pierre-Ernest Weiss. In a non-magnetised ferromagnetic material, the magnetic orientation of the individual magnetic domain is random. When an external magnetic field is applied to a ferromagnetic material, the magnetic domain align themselves parallel to it until the material is completely magnetized. This happens because the transition areas between the magnetic domains, the so-called Bloch or Néel walls, shift. The reorientation increases in speed with increasing field strength until magnetic saturation is reached. When the magnetic orientation of the external magnetic field changes, the same magnetization process occurs. This is called hysteresis.
The curve progression of a hysteresis is material-specific. There are significant differences in the magnetization process between hard and soft ferromagnetic materials. Since the crystalline microstructure influences the magnetic microstructure and is decisive for the mechanical properties, the mechanical hardness of ferromagnetic materials can be determined by measuring their micromagnetic properties. The higher the Barkhausen amplitude, the magnetically and mechanically softer the ferromagnetic material is.
The µmagnetic measuring system tests the hardness of ferromagnetic materials contactlessly and non-destructively. The measuring system applies an external magnetic field to the material to be tested and simultaneously analyses the reaction of the ferromagnetic material. The magnetic orientation of the external magnetic field is changed up to several hundred or thousand times per second in order to cause repeated hysteresis reactions. The simultaneously acquired Barkhausen signals are evaluated in real-time through Fast-Fourier transform and spectral analysis. Adaptive spectral filters ensure dynamic suppression of interference signals during analysis.
The measurement results of the hardness test are visualized live in a 3D-spectrogram. The determination of a numerical hardness value, e.g. in Rockwell, Brinell or Vickers, is possible after a single calibration. The measuring system automatically detects if the specified tolerance limits are exceeded and initiates a predefined event.
The µmagnetic measuring system can be used to determine the hardness of ferromagnetic materials under production conditions. It can be integrated into all process stages of production. Hardness testing in motion is possible with rotational or linear movements. With our QOBOT handling system specially developed for µmagnetic technology, the hardness of components of different geometries and lengths can be tested automatically. The QOBOT is individually adapted to the process and the production environment by QASS.
Non-contact, non-destructive and in real-time
With our µmagnetic measuring system you can test the hardness of ferromagnetic materials contactless and non-destructive. Real-time spectral analysis makes the properties of your material visible live.
100% instead of random sampling
Our µmagnetic technology can be integrated into all process stages of production. Be it material or mix-up tests before the first manufacturing step or quality tests in or at the end of the manufacturing process – with the µmagnetic you can completely test your materials and components, because our measuring method does not work destructively.
Customer- and process-specific solutions
QASS ideally adapts the µmagnetic measuring system to your process and hardness testing requirements. If you need a special sensor design, we will develop it for you. If you need an individual handling system, we will set up the QOBOT perfectly for you.
Our R&D team is constantly developing the µmagnetic technology further. Use the µmagnetic measuring system and be ahead of the competition.